Pigment compositions



Patented Dec. 14, 1948 'assignor to E; 1?; do PontJ-d'e Nemouts.&Company, Wilmington; Del.,

aicnm oratiomof Bela-:1

N Drawing. Application February I6, 1944 SeriarNo. 522,667

7 1; This'invention,relatesto metallic pigmenteompositions," and more?particularly to. improved coating compositions and films therefrom containing flaked metalpigment.

"Metallic paints are of considerable technical importance: It has longbeen known. that, in order-toobtain metallic coatings of high brightness(desirable in the production-ofyartisticaffects andof certain physicaleffects such as: the reduc tion of heat reflectance-from hot surfaces)the metal flakes in the paint film showtime-oriented, i. e.,a-largeproportionof the flakes: should-lie in the s'amedirectionwithrespect to the plane of the film-rather than in-all directionsat-rand-om. In general, the brightness of the film ispropor tional tothe degree oforientation; also: called lea'fing. I

As disclosed in application Serial No. 5221666 now 'maturdintoPatent-No.2,418,479, filed of even date herewith by myself and Paul L. Salzberg,it has been found that ferromagnetic flake, on mixtures; offcrromagneticflake andnon-magnetic pigment, can be orientedinzafilmrcontaining the same by rotating the film in the plane of amagnetic field;

This invention has as aniobiect the production of new flake metalpigment. compositions; Arturther object is the provision ofpigmentscomprising: noneferromagnetic. flake metal which; is responsivetothehactionof. a magnetic field. A still further object is themanufacture of valuable film-forming compositions containing fiakemetalpigment. Other objects will appear hereinafter.

The above objects are accomplished by preparing in the manner moreparticularly described hereinafter mixtures of finely dividednon-magnetic flake metal pigment and ferromagnetic pigment, and by theformulation of compositions comprising these pigment mixtures and afilmforming vehicle.

Although the flake of the metal pigment mixtures described herein can beoriented or leafed by the usual methods of brushing or knifing in filmformation, the compositions of this invention are of particular value inconnection with the magnetic method of orientation previously referredto because very high orientation can. be obtained in films in which thepigment consis preponderantly of non-ferrous metal.

In the preferred practice of the invention the non-magnetic pigment iscoated with the magnetic pigment, as shown in Example I below, since theresponsiveness of the total pigment to a magnetic field is enhancedthereby. However, this is not essential, and an intimate mixture ofaciaims. (ch ne-29o). I

non-magnetic and magnetic pigments; as; shownimExampleaIhihasgbeemfounditorbawellladapted to;magnetic-orientations' IThe invention is illustratedv by the; following examples: in: which.parts are; by, weight. unless otherwisespecified;

Example I.

AsmiXture-.-o.f 50,-parts, of magnetite (magnetic ironoxide) and: 4.0.partsrof a hydrocarbomplasticizer marketed; by the Wilmington; ChemicalComhany 'underg-the trade, name Naitolen, Ila- 100? andlu onsistine. ofaromaticand cycloaliphatic hydrocarbons is milledmna-iiroll-millineufficient passes; to -.nroduc.e; a well; dispersed: paint... Sixparts of. the resulting; paint, is addedzwithlstirring to a, paste. of,30.-par,ts-, of fineg aluminum: bronze pnwderlflake), in'i35lparts of;carbontetrachloride; After; the-composition is well mix-ed, 27-vparts'of; a. -.15 ,siolution of; nolystyrenaim xylene, hpartsof;thersame;hudrocarboniplasticizer: and; 25; parts ofearl:onztetrachloriderareaadded andzthezmixture isstirreduntilihomogeneous;. ..'Ilhe:resultineinainta in. which.the;magnetite/aluminumi powder ratio is; 1-0 /9 0,@. the.pigment/binderratio. is; Id/25tand thepolystyrene/plasticizenratio" is;40/60,: has. a VlSCOSi-tXxSllitQblQ for knife-coating;

rmm zau.

Amixture of ii: parts of "Perr'nalloy flake" (a magnetic-alloy ofiron'and'nickel), 33 parts of fine aluminum bronze powder-- (flake) and20 par-ts ofxylene is groilnddna mortar 'for 10 minutes." Thirty partsofxylene and pa-rts-of-a 25% solution of polystyrene in xylene are addedand the paint is stirred until homogeneous. The resulting paint, whichhas a pigment/binder ratio of /25 and a Permalloy/aluminum powder ratioof 25/75, has a suitable viscosity for film preparation by spinning, i.e., pouring the paint on a rotating disc, as described in GardinersPhysical and Chemical Examination of Paints, 1939, page 98.

One method of applying the above mentioned method of magneticorientation consists in rotating the wet paint film between and inparallel relation to the poles of a magnet until it has driedsufficiently to permit removal from the field without causingdeorientation of the flakes. As an example, a 20 mil coat of the paintcomposition of Example I is knifed on Cellophane attached by rubbercement to a 5" Bakelite disc. The disc is placed on a turn-table mountedbetween two electromagnets actuated by 220 volt direct current in such aWay that a film'placed thereon is ap- 3 proximately in the center of thefield. The turn-table is rotated at about 30 R. P. M. The magnetic fieldis applied at a strength of about 100 gauss. The film is rotated for onehour. then air-dried overnight, after which the Cellophane is stripped'fromthe Bakelite, soaked .in water for one hour, and finally strippedfrom the pigmented film. The resulting detached film is pliable,stronger and brighter than a control film 1;;

prepared outside the magnetic field.

Likewise, a film is prepared by pouring a por-' tion of the paint ofExample II on a5 paper disc rotating at 250 R. P. M; The paper disc-mments of this" invention may be made without deis transferredimmediately to the turn-table, which is rotated for one hour at 30 R. P.M. in a magnetic field of about 100 gauss. A second coat, of paint isthen applied and the procedureree preferred that they contain enoughferro-magnetic pigment to render the pigmentmixture' responsive to theaction of a magnet of practical field strength, i. e.,- between 5and5000gauss', in a vehicle of practical viscosity. l i 1 Theintimatemixturesof non-magnetic and magnetic pigments described'herein canbeobtained by several methods, such as grinding the dry pigmentstogethen mixing their dispersions in film-forming vehicles'or involatile'solvents, evapcrating a suspension of a magnetic pigment on 407 the surface of the nonmagnetic flake pigment particles, pounding intoflakes a massive mixture of nonmagnetic and magnetic metal, etc. Incertain cases special methods are used. For example, an aluminum-ironalloy can be pounded into flake form; then treated with sodiumhydroxidewhich dissolves the aluminum on the surface ofthe' flakes,leaving a surfaceof. ferromagnetic iron.

The pigment compositions can b formulated into paints with-anydesired-film vehicle such as drying oils, varnishes, the various alkydresins, amide-formaldehyde resins, polyethylene, poly-.- isobutylene,nitrocellulose, methyl cellulose, polyvinyl alcohol, etc.. For practicalpurposes, the

vehicle should have a viscosity of at least 0.3 poise at 25 C. The paintcompositions can contain other ingredients such as plasticizers,fillers, dispersing agents, non-metallic pigments, dyes, etc.

The presentcompositions are useful in all applications whereinetallicpaints are desired. The invention is, as previously noted, of specialvalue 'F'iIl providing compositions yielding high orientation oftheflake by magnetic means and hence bright films from flake pigmentcomprising a ,largeproportion of non-magnetic pigment.

-As; many apparently widely difierent embodithe specific embodimentsthereof except as defined in the appended claims.

Iclaim:

1. A pigment composition the pigment content of which consistsessentially of; a mixture of discrete particles cinch-magnetic flakemetalpig: ment with discrete particles of ferromagnetic metal pigmentand in which substantially all the metal flakes contained in saidcomposition are susceptible to magnetic orientation when contained in anundried paint film, said pigment composition containing in preponderantamount thin aluminum flake pigment and from 10% to 25% by weight of .thepigment mixture of ferromagnetic metal pigment; J2. la-coatingcomposition comprising a film. forming vehicle, av solvent andthemixture of non-magnetic flake pigment and ferromagnetic metal pigmentdefined in claim 1. I

g 3. The pigment composition defined in claim 1 in which saidferromagnetic pigment is a magnetic alloy of iron and nickel.

- i BURT CARLTON PRA'I'I'.

, REFERENCES CITED The following references are of record in the file ofthis patent: l

UNITED STATES PATENT$ Number 1 Name Date -2,184,769 Alexander Dec. 26,1939 1,726,340 Buttles Aug. 27, 1929 1,292,206 Woodruif Jan. 21, 1919FOREIGN PATENTS Number Country Date 226,286 Heskett .'Dec. 22, 1924Certificate of Correction Patent No. 2,456,313. December 14, 1948.

A BURT CARLTON PRATT It is hereby certified that error appears in theprinted specification of the above numbered patent requiring correctionas follows:

Column 3, line 53, for the word methyl read ethyl;

and that the said Letters Patent should be read with this correctiontherein that the same may conform to the record of the case in thePatent Oflice.

Signed and sealed this 19th day of April, A. D. 1949.

THOMAS F. MURPHY,

Assistant Gammz'sszoner of Patents.

